The invention relates to fuel management systems for internal combustion engines. More particularly, the invention relates to a fuel injection system for engines in which there are disposed electromagnetic fuel injection valves that are actuated by control pulses that are generated by a suitable control pulse generator. The frequency and duration of the valve-actuating pulses depend on the engine speed, the inducted air flow rate and other secondary variables such as, for example, engine temperature. Additional engine conditions affecting the valve control pulses may be engine starting, the barometric pressure of the ambient atmosphere and the pulse generator may include a provision for suppressing or sharply reducing the fuel control pulses whenever the vehicle is being operated in downhill use, i.e. when the engine delivers negative torque. This condition is detected as a combination of events, namely that the throttle valve of the engine is closed whereas the engine speed rises above a predetermined minimum. The known fuel injection system and its pulse generator may suppress the valve actuation pulses during engine braking and thus entirely suppress the fuel supplied to the engine. In the known system, when engine braking ends, the system reverts to normal operation, i.e. to the generation of normal control pulses. It may happen however, especially when the engine has been operated in downhill operation or in engine braking for a substantial length of time, that the induction tube is cooled off substantially so that the injected fuel is condensed on the cold interior surfaces of the induction tube and the cylinder walls in which case the resulting mixture will not be optimally combustible and the engine will run rough and tend to generate toxic exhaust gas components, in particular hydrocarbon emissions.